This paper presents an algorithm to determine the angular dependence of the transmittance and reflectance of homogeneous glazing layers given the reflectance and transmittance at normal incidence, the wavelength, and the thickness. For the commonly used solar and visible properties, typical wavelengths are presented that can be used with this procedure to approximate these wavelength integrated properties. Theoretical calculations have shown that the absolute error of this approximation is less than 1.5% for most clear, low-iron, and absorbing glasses. Existing approximations can yield absolute errors up to 15%. This new approximation can be used with computer programs that calculate energy fluxes through glazing(s) based on the glazing thickness and optical properties at normal incidence.